In mammals, micturition (urination) is a complex process that requires the integrated actions of the bladder, its internal and external sphincters, the musculature of the pelvic floor, and neurological control over these muscles at three levels (in the bladder wall or sphincter itself, in the autonomic centers of the spinal cord, and in the central nervous system at the level of the pontine micturition center (PMC) in the brainstem (pons) under the control of cerebral cortex) (De Groat, Neurobiology of Incontinence, (Ciba Foundation Symposium 151:27, 1990). Micturition results from contraction of the detrusor muscle, which consists of interlacing smooth muscle fibers under parasympathetic autonomic control from the sacral spinal cord. A simple voiding reflex is formed by sensory nerves for pain, temperature, and distension that run from the bladder to the sacral cord. However, sensory tracts from the bladder also reach the PMC, resulting in the generation of nerve impulses that normally suppress the sacral spinal reflex arc controlling bladder emptying. Thus, normal micturition is initiated by voluntary suppression of cortical inhibition of the reflex arc and by relaxation of the muscles of the pelvic floor and the external sphincter. Finally, the detrusor muscle contracts and voiding occurs.
Abnormalities of lower urinary tract function, e.g., dysuria, incontinence, and enuresis, are common in the general population. Dysuria includes urinary frequency, nocturia, and urgency, and may be caused by cystitis, prostatitis or benign prostatic hypertrophy (BPH) (which affects about 70% of elderly males), or by neurological disorders. Incontinence syndromes include stress incontinence, urgency incontinence, and overflow incontinence. Enuresis refers to the involuntary passage of urine at night or during sleep.
Prior to the work of the present inventors, treatment of neuromuscular dysfunction of the lower urinary tract has involved administration of compounds that act directly on the bladder muscles, such as flavoxate, a spasmolytic drug (Ruffman, J. Int.Med.Res. 16:317, 1988) also active on the PMC (Guarneri et al., Drugs of Today 30:91, 1994), anticholinergic compounds such as oxybutynin (Andersson, Drugs 35:477, 1988), or “mixed action” drugs like imipramine (Andersson, Drugs of Today 24:337, 1988). The use of α1-adrenergic receptor antagonists for the treatment of BPH is also common but is based on a different mechanism of action. (Lepor, Urology, 42:483, 1993).
However, treatments that involve direct inhibition of the pelvic musculature (including the detrusor muscle) may have unwanted side effects such as incomplete voiding or accommodation paralysis, tachycardia and dry mouth (Andersson, Drugs 35:477, 1988) and drugs like imipramine may have relevant side effects, in particular on the cardiovascular system (orthostatic hypotension, ventricular arrhytmia) at the therapeutic doses. Thus, it would be preferable to utilize compounds that act via the peripheral or central nervous system to, for example, affect the sacral spinal reflex arc and/or the PMC inhibition pathways in a manner that restores normal functioning of the micturition mechanism.
Flavoxate, oxybutynin and imipramine are representative drugs from three different classes of compounds currently used in the therapy of urinary incontinence. These drugs have been tested in animal models where their activity has been confirmed.
The compounds of the invention, described below, have few structural characteristics in common with the above cited drugs, other than a basic nitrogen atom.
The compounds of the invention are more potent, relative to the above cited drugs, in pharmacological tests predictive of activity on the lower urinary tract, in particular for activity against neuromuscular disfunction of the lower urinary tract. The compounds of the invention are also potent and selective ligands for the 5-HT1A serotonergic receptor.
Other compounds which have been discovered by the present inventors to be useful in the methods of the present invention, e.g., treatment of disorders of the urinary tract, are disclosed in French Patent 1,505,109; EP 479,546; DE patent 2,800,535; Arch. Pharmacie. 328:604 (1995); Arzn. Forsch. 31:1178 (1981) and J. Med. Chem. 2:860 (1969), all of which are incorporated by reference.